Technical Field
This disclosure generally relates to the reconfiguration of select elements of a power distribution network to reduce losses inherent in traditional use of local soil or “earth” as the “ground” or neutral wire as a return path to close a supply circuit, while also reducing voltage instability.
Description of the Related Art
It is well known that three (3) phase systems may or may not have a neutral wire. A neutral wire allows the three (3) phase system to use a higher voltage, while still supporting lower voltage single phase equipment. In high voltage distribution, it is common not to have a neutral wire since the loads can simply be connected between phases of the source. However, 3 phase systems may use a fourth (neutral) wire, particularly in medium and low-voltage distributions where typically single phase step down transformers (SDTs) are installed. The neutral wire allows three separate single-phase supplies to be provided at a constant voltage, and is commonly used for supplying groups of domestic properties which are each single-phase loads. The connections are arranged so that, as far as possible in each group, equal power is drawn from each phase. Further up the distribution system, the currents are calculated to be balanced in each phase but in reality they are usually not well balanced. Transformers may be wired in a way that they have a four-wire secondary but a three-wire primary, allowing unbalanced loads and the associated secondary-side neutral currents. According to modern electrical code, each supply circuit has a ground wire that returns to the distribution panel and that is connected to a 10 foot long metal grounding rod driven into or buried in the local soil, outside but within approximately 10 feet of the footings of a structure. The distribution panel is typically connected to an overhead or underground supply circuit comprised of 2 or 3 conductors, limited to 100 or 200 Amp capacity. In some cases, the “neutral” or “return” conductor is grounded, but in other cases it is floating, with a separate ground conductor supplied for safety, permitting ground fault interruption devices or components to be included in certain circuits. These safety circuits should be separate from the supply.
Conventional (North American) electrical power distribution systems include a medium voltage three (3) phase trunk line crossing through a prospective service area. Over time, an increasing number of branch lines tap into that trunk line and are directed toward developing (e.g., industrial, commercial and residential) communities. These developing communities typically develop somewhat randomly, sprouting “leaves” comprised of step down transformers (SDT) and an ever increasing number of low voltage loads drawing greater amounts of energy. The electronic portion of these loads tends to be less tolerant of voltage instability. The resulting “tree like” assembly of circuits is commonly referred to as an electrical network or power grid.
Conventional electrical power generation equipment delivers a sinusoidal signal to the three (3) conductors comprising the above trunk line. The amplitude of that signal is typically higher at the source and along the trunk (sometimes known as—line voltage), then stepped down to lower medium voltage (sometimes known as—phase voltage) on the branch lines, then stepped down again to low voltage for consumption at the load sites. For a given power flow, as voltage decreases current increases, such that “heating” losses increase as higher currents must flow through more resistive media closer to the loads. At the same time, consumers of electrical energy switch their loading devices ON and OFF, respectively, drawing more and then less energy collectively. This causes dips and then surges of available energy on the distribution network. Many of the loads and modern service panels implement a “floating ground” at the load site, where dedicated neutral or return conductors are hard wired to close each circuit internally and the “ground” conductor is relied on for safety purposes to divert stray (including ground fault) currents away from users. In the many load sites, the step down/low (e.g., 120/240) voltage supply transformers are also installed with a dedicated ground conductor, between the service panel and the secondary of the SDT supplying that panel, as well as a hard wired neutral or return conductor back to the applicable SDT.
However, as energy consumption and delivery costs increase, there are still a number of load sites relying on an earthen form of ground (e.g., a metal stake driven into or buried in the local native soil in proximity to each of the SDT and its service panel) between the service panel and the secondary of the SDT supplying that panel. Moreover, some of those sites also use a grounded neutral to effectively close the return circuit through the service panel to the SDT for that site.
Further, even in connection to modern load sites having dedicated conduits for their grounding and (electrically isolated) return circuits, there exists the larger legacy problem of using an earthen ground on both the branch and trunk portions of that distribution network, to close those return circuits.